Plug and barrel assembly for marking device

ABSTRACT

A writing instrument is provided with a combined decorative and functional ring or band at the juncture between the plug and the barrel of the reservoir section of the instrument. The ring or band cooperates with means on the plug to effect a locking and a sealing relationship between the plug and the barrel.

[l5] 3,659,953 45] May 2, 1972 United States Patent Taylor [54] PLUG ANDBARREL ASSEMBLY FOR 2 0 H m "S N m T "A m ML m mA I. R no S m a n m am 54 s 3 MARKING DEVICE 3 8 4M 9 22 l ll 1 00 v 80 6% cc 33 It GFFG 4 666fl66 9999 III UMU6 8204 9872 .9 888 6884 4 9 l .v. H n I m. .m m v 0 ct h B r, 0 h W7 v. 9 GR T .M In y mr u a n. GSA m a t n: 5 58 v S .mAF1]] 232 772 .l.[[

[2]] App]. No.: 30,518

Primary Examiner- Lawrence Charles H "Am/198, 401/243 Attorney-Hofgren,Wegner, Allen, Stellman & McCord .40l/l98, 202, I99, 196, 243-247,

I52] U.S.Cl............. I

ABSTRACT A writing instrument is [58] Field olSearch.........

provided with a combined decorative and functional ring or band at thejuncture between the plug and the barrel of the reservoir section of theinstrument. The

References Cited 38 m d n ma m an. M 6 M n m W e ow n S 8 m m e.@ W m mMb 4 wm M m r 8 mm C PM 3 mm 1 c a d 0 mm mm mm a nbb 433 444 HER 111000 S m T m N m E u T m A u. P W: S n E me m m T mm S 88 D HHM E n 531 N603 U 999 ill Ill 33 637 9 8 X29 728 3 1 Patented May 2, 1972 INVENTORATTORNEYS BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to writing instruments and more particularly to awriting instrument having at least two plastic parts sealed and latchedtogether in an effective and decorative manner.

2. Description of the Prior Art Writing instruments and in particularwriting instruments with wick-type or porous nibs have been known forsome time. The numbers of different types of such instruments have beenincreasing so that it is becoming competitively important to provide notonly a better appearing instrument, but also a less expensive and higherquality instrument. Certain manufacturers have provided a decorativemetal band or ring around the barrel of the instrument generally at thejuncture of the barrel with the end plug. Although the ring does enhancethe appearance of the instrument, it performs no useful function, addscost and at times contributes to a poor seal between the end plug andthe barrel.

Currently two plastic parts of a writing instrument, such as the endplug and barrel, are secured together in many different ways, one suchway being spinwelding wherein the two parts are spun relative to eachother until the frictional heat melts and fuses the plastic materialtogether. Another method entails the use of chemicals in the form ofadhesives or material attacking agents which require long set-up timeand careful control during application and setting. A third such methodis mechanical wherein the parts are press-fitted together. To beeffective this method requires relatively thick wall components andcareful tolerance control. The last common method is the use ofultrasonics wherein a sound frequency is directed at the area to beconnected for melting and fusing the plastic parts together.

Each of the four enumerated methods of attachment is limited in itsapplicability to the current problem because of the high costs of theequipment to effect the connection (spinweld and ultrasonics), becauseof the increased costs due to slow production time (adhesives, etc.) orbecause of the in creased material costs and resulting designlimitations (mechanical connections).

SUMMARY OF THE INVENTION The writing instrument involved in the presentinvention generally includes a hollow barrel for housing porous materialimpregnated with a marking fluid. A wick-like or porous nib projectsfrom one end of the barrel, or from a ferrule associated with thebarrel, and the inner end of the nib engages the impregnated porousmaterial. Thus the porous material in the barrel constitutes an inkreservoir for the capillary flow of ink through the nib to the surfaceto be marked. The general structure of the writing instrument, exceptfor the present invention, is as shown in the Design Patent of Walter J.DeGroft, entitled Writing Instrument, Des. Pat. 217,646, issued May 19,1970 therefor.

The present invention is more particularly directed to a writinginstrument of the above described type which has at least two plasticparts which are joined together to form the hollow reservoir or barrelthereof for the ink supply. The junction of the two parts ischaracterized by a decorative ring or band on one part coacting withmeans such as a bead or beads on an interfitting portion of another partto effect a latching and sealing relationship between the two parts. Thetwo parts are assembled by mechanically forcing the portion of one partinside the other until the means, e.g. an annular bead, on the one partbecomes positioned with respect to the ring or band to latch and sealthe two parts together.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partial perspective viewof one end portion of a writing instrument incorporating the invention;

FIG. 2 is an exploded view of the parts of the end portion of theinstrument of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the instrument taken alongthe line 3-3 of FIG. 2; and

FIG. 4 is a greatly enlarged cross-sectional view taken along the line4-4 of FIG. 1 showing the relationship between the parts.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawingswherein like reference numerals refer to like parts throughout theseveral views, a writing instrument 10 shown only in partial view iscomposed of an elongated, hollow barrel 12, a hollow end cap or plug 14and a retaining ring or band 16. The illustrated embodiment is a writinginstrument of the type having a wick-like or porous nib, and therefore,there is shown a quantity of absorbent material affording a reservoirelement 17 in the barrel l2 and end cap 14. It is to be understood thatthe interior of the barrel and end plug will house the reservoir element17 which is impregnated with marking fluid to afford a large supplysource of marking fluid.

The barrel I2 is molded or otherwise fonned of a plastic material suchas polypropylene, and is a relatively thin-walled construction. Thebarrel I2 is provided with an end portion 20 having an open end 18 andan inner annular wall portion shaped to make a close mating fit with askirt portion on the plug 14. The end of the barrel l2 opposite to theopen end 18 is provided with any one of the known nibs, tips or pointsused for writing on a surface. The end portion 20 has exteriorly areduced diameter recessed portion 22 extending a short distance axiallyof the barrel to afford an external annular seat for the band 16 as willbe more fully described later. Internally the end portion 20 of thebarrel has a pair of differing diameter step portions 24, 26, with thestep portion 24 having both an axial dimension and a diameter largerthan the axial dimension and the diameter of the step portion 26.Portion 26 has a diameter which is larger than the internal diameter ofthe major axial portion of the barrel 12. Between step portions 24 and26 is a shoulder 28 and between the step portion 26 and the interior ofthe barrel 12 is a shoulder 30.

The end cap or plug 14 is preferably molded or otherwise formed of aresilient material such as plastic of the polypropylene type. The plug14 has a slightly tapered outside wall 32 and an integrally formedclosed end 34. The other end portion or skirt 36 of the plug 14 is atleast slightly resilient and has three axially extending reduceddiameter step portions 38, 40 and 42 formed in the outside wall thereof.The first step portion 38 is separated from the outside wall 32 by anaxially facing shoulder 44 and has a continuous annular raised bead 46formed approximately midway along the axial extent of said portion 38and is generally concentric with respect to said shoulder 44. The secondstep portion 40 is separated from the larger diameter step portion 38 bya shoulder 48 and has a shoulder 50 separating the other end of saidportion 40 from the smallest diameter step portion 42. Intermediate stepportion 40 preferably has a continuous annular raised bead 52 formedapproximately midway along the axial extent of said portion and lyinggenerally concentric with respect to the shoulders 48 and 50. Sometimesin practice it has been found that bead 46 should most advantageously beslightly larger in axial and radially projecting extent as compared tothe bead 52 for a reason to be more fully disclosed hereinafter.

The internal diameter of the internal step portion 24 of the barrel 12is substantially equal to or slightly smaller than the external diameterof the external largest diameter step portion 38 of the plug 14; and theinternal diameter of the internal step portion 26 of the barrel 12 issubstantially equal to or slightly smaller than the external nextsmaller diameter step portion 40 of the plug 14. Finally, external stepportion 42 of the plug 14 has a diameter substantially equal to orslightly larger than the internal diameter of the major body portion ofthe hollow barrel 12.

The ring I6 is a band of material, preferably metal and in most caseswill have an outside surface 54 of some decorative,

contrasting color. The ring or band 16 is a shaped part being somewhatinverted L shape in cross section. The axial leg portion 56 is generallycylindrical in shape to reinforce the underlying resilient plasticportions of the barrel l2, and it is provided with an axial end 58 whichis preferably tapered (as shown in FIG. 4) although it may be square(not shown). Whatever the shape of the end 58 it should substantiallycoincide with the shape of the axial end wall or shoulder 60 of therecess or seat 22. The horizontal leg or flange 62 of the ferruleextends radially inward from the axial leg portion 56 and has an openingwith an internal diameter which is equal to or larger than the internaldiameter of the step portion 24. The ring 16 is slipped over the end 18of the barrel 12 with the leg or flange 56 resting in the recess 22thereof. The end 58 of the leg 56 of the ring 16 rests against the wallor shoulder 60 of the barrel as the radial leg 56 of the ferrule restsagainst the end 18. Since the internal diameter of the leg 56 is equalto, or greater than, the internal diameter of the step portion 24, theleg 56 of the ring 16 will not extend inwardly into the barrel 12.

In assembling the end cap or plug 14 with the open end portion 20 of thebarrel 12, which barrel has the ring 16 in place in the recess portion22 as has been heretofore described, the smallest diameter step portion42 is aligned with and inserted into the opening in the ring 16 and theopen end of the barrel 12. During axial movement of the plug 14 into thebarrel, it is understood that adjacent resilient plastic parts will eachbe mutually resiliently compressed and expanded where plug portions areslightly over-sized. The movement of the end portion 36 of the plug 14into the end portion 20 of the barrel will be without resistance untilthe end of step 42 engages with the shoulder between internal stepportion 26 and the interior of the barrel 12. At that point pressure onthe end cap or plug 14 axially of the barrel 12 will cause slightexpansion of the barrel and will cause the material of the end cap orplug to resiliently compress permitting the step portion 42 to slide ashort distance axially into the end portion of the barrel until the bead52 engages with the shoulder 28.

Continued axial pressure similarly will compress the external smallerdiametered intermediate step portion and the head 52, and will compressand expand adjacent portions of the inner wall of the barrel 12, untilthe bead 52 slides past the shoulder 28. About the time the bead 52passes the shoulder 28 the resilient bead 46 will engage with the edgeof the opening in the ring 16 and continued axial pressure willresiliently compress the raised bead 46 and largest diarnetered externalstep portion 38 until the head 46 passes axially into the internal stepportion 24. At this time the bead 46 is resiliently com pressed, andadjacent inner wall portions of the barrel 12 are resiliently compressedand expanded to a lesser degree because they are reinforced by theannular leg 56 of the ring 16,

As the end plug 14 is pushed farther into the barrel, as shown in FIG.4, the midpoint of head 46 will preferably axially pass a small distancebeyond the reinforcing annular leg 56 of band 16 and its end 58; and inthis position, the nonoverlapping portion of the resiliently compressedbead 46 will radially outwardly expand into material compressing andexpanding relationship with that portion of the barrel adjacent thetapered end 58 of the ring 16, while the overlapping portion of the bead46 and ring 16 will tend to expand the barrel portion underlying thering 16 to create an exceedingly effective latching and sealingrelationship between the end plug and the barrel.

The effective latching results from the forces created by the expansionof the bead 46 beyond the end 58 of the ring, and in order to remove theend plug from the barrel, sufiicient separating pressure must be createdto compress the bead 46 within the confines of the barrel and itsreinforcing ring. It takes considerable more separating force to partthe plug from the barrel especially when you consider the small smoothdifficult-to-grip surfaces of the two parts.

in addition, the partial overlap of the bead 46 with the ring 16 createsnot only radial expansive forces in the ring encased portion of the step24 of the barrel but also it creates axial compressive and expansiveforces between the area of the bead indenting into the plastic step 24and the horizontal leg portion or flange 62 of the ring 16 tending toincrease the latching effect between the end plug and the barrel.

The positive sealing effect between the end plug and the barrel isaccomplished in a threefold manner herein. First, the seal created bythe expansion of the beads 46 and 52 into the respective steppedportions 24 and 26 of the barrel; and, second, the seal created by thepartial overlap of the bead 46 with the end 58 of the leg 56 of the ring16 creating the relative compressive and expansive sealing effectsbetween the barrel step portion 24 within the ring leg 56 and flange 62and the end plug. The third seal is created by the substantialcoincidence between the diameters of the barrel and the smallestexternal diameter step portion 42. That is, the diameters of the portion42 and barrel are uniform throughout their over lapping axial length soas to avoid openings of a capillary nature. Because of the effectiveseal, the ink impregnated reservoir can be expanded to include thevolume of the hollow plug, as shown in FIG. 3 without fear of leakage atthe juncture of the plug and barrel.

The band or ring 16 serves not only the purpose of being decorative butalso restricts the outward expansion of the thin walled end of thebarrel. Plastic is known to fatigue and to cold-flow when deformed overa period of time, and it may crack when expanded beyond the limits ofits resiliency. The reinforcing ring 16 of the present invention aids inthe solutions obviating all of these problems. Furthermore, by using thering as a reinforcement, it is possible to reduce the thickness of thebarrel walls of the writing instrument thereby increasing the volume ofthe writing fluid in the writing instrument and the usable life andvalue of the instrument. Reducing the wall thickness also reduces theamount of material needed to mold the instrument thereby reducing thecost of making the device. The thinner walls require less cooling timein the molding cycle and therefore the speed of manufacturing is increased further reducing the cost of making the device. Finally, byhaving an efi'ective seal and latching at the juncture of the plug andbarrel, the open end of the barrel adjacent the plug can be used toconveniently place the absorbent material of the reservoir into thebarrel during one of the steps of assembly in manufacturing.

The invention clearly accomplishes the prime objectives of providing animproved instrument which is substantially trouble free from a leakingstandpoint while at the same time mak ing use of one of the simplestmethods of assembly, namely, mechanical assembly. In addition to theimproved results created by the invention, a writing instrument isproduced which is cheaper in material and manufacturing costs, and whichprovides a larger internal reservoir and therefore a longer writingcapability.

I claim:

1. In a writing instrument of the type having a reservoir for markingfluid, a plug and barrel assembly, and a writing means on said barrelassembly, comprising: an elongated hollow barrel having an inner chamberto house the reservoir and being provided with an annular open endportion of resilient material, said barrel having the writing meansmounted on the end opposite said open end portion, the end portionhaving an annular inner wall portion; a plug member closed at one endand having an annular resilient skirt positioned within the open endportion of the barrel and shaped to make a close mating fit within saidannular inner wall portion, said skirt having an annular outwardlyextending continuous bead shaped similarly to the contour of the skirtand making a continuously contacting resilient sealing fit against saidannular inner wall portion; and an annular retaining ring positionedabout the annular open end portion of the barrel to restrain expansionof the underlying inner wall portion, said ring being positioned betweenthe outwardly extending bead and the open end of the barrel to latch thebead of the plug member in sealing relation against the inner wallportion of the barrel.

2. A plug and barrel assembly as specified in claim 1 in which the beadis positioned longitudinally inwardly of the open end of the barrelbeyond the position of the retaining ring and in partially overlappingrelation with respect to said ring.

3. A plug and barrel assembly as specified in claim 1, in which theskirt portion is provided with a cylindrical reduced diameter stepportion in its outer surface, and the inner wall portion iscylindrically shaped and of substantially the same diameter as said stepportion, the outwardly extending bead being circular and being locatedintermediate the ends of said cylindrical reduced diameter step portion.

4. A plug and barrel assembly as specified in claim 1 in which the innerwall portion of the barrel is provided with interior plural differentdiameter step portions, and the annular skirt of the plug is providedexteriorly with corresponding plural different diameter step portions,the corresponding step portions being shaped to make a close mating fitof the skirt within the open end portion of the barrel.

5. A plug and barrel assembly as specified in claim 4 wherein saidcontinuous annular bead is formed on the exterior of one of said stepportions of said plug for sealing with a corresponding interior stepportion in the inner wall of said barrel.

6. A plug and barrel assembly as specified in claim 1 wherein theretaining ring has a cylindrical portion nested in a recess in theexterior surface of the open end portion of the barrel and an integrallyformed, radially inwardly directed flange portion overlying the end edgeof said open end portion of the barrel whereby the latching forcecreated by said bead compresses the material of the end of the barrelgenerally axially against said flange of the ring and generally radiallyagainst the cylindrical portion of said ring.

7. In a plug and barrel assembly as specified in claim 1 wherein thematerial of the barrel and plug is plastic and the walls of said barrelare relatively thin.

8. A writing instrument having a barrel with one open end and with awriting means projecting from the other end, a plug assembled with theopen end of said barrel, and means for latching and sealing said plug inthe open end of said barrel, said means comprising plural differentdiameter step portions on the exterior of the open end portion of saidplug, outwardly extending continuous beads formed on at least two stepportions on said plug, plural different diameter step portions formed onthe interior of the open end portion of said barrel, the diameters ofthe corresponding step portions on the plug and in the barrel beingsubstantially equal, an annular retaining ring having a cylindricalportion encircling the exterior open end portion of said barrel, thebead on the largest diameter step portion of the plug being positionedin partially overlapping relationship with the remote end of thecylindrical portion of the ring thereby compressing the correspondingstep portion of the barrel into a latching end sealing relationship withsaid plug, and a second seal being efiected between the barrel and theplug by said bead on the next largest diameter step portion of the plugindenting into the material of the corresponding step portion of thebarrel whereby the barrel and plug are securely latched and sealedtogether.

9. A writing instrument as claimed in claim 8 wherein said ring has aradially inwardly directed flange portion overlying the end of thebarrel whereby the latching and sealing created by the bead on thelargest diameter step portion is effected in the material of the barrelby the axial and radial compressive forces created between the flangeand cylindrical portions of the retaining ring and said last named bead.

10. A writing instrument as claimed in claim 8 wherein the diameter ofone step portion of said plug coincides throughout its length with acorresponding substantially equal in diameter internal portion of saidbarrel whereby sealing against capillary leaking therebetween iseffected.

11. A writing instrument as claimed in claim 8 wherein the material ofthe barrel and plug is a plastic material and the material of saidretaining ring is a metal material.

12. In a writing instrument having an elongated, hollow barrel made ofplastic material and with one open end and with a porous writing nibprojecting from the other end, a cap frictionally and removably attachedto said barrel in covering relationship to said writing nib, and a plugmade of plastic material and having one end closed and having the otherend open, said open end of the plug being assembled with the open end ofsaid barrel, in combination, means for latching and sealing said openend of said plug in the open end of said barrel, said means comprisingplural different diameter step portions on the exterior of the open endof said plug, an outwardly extending continuous bead formed on thelargest and next largest diameter step portions of said plug, pluraldifferent diameter step portions formed on the interior of the open endportion of said barrel, the diameters and axial lengths of thecorresponding step portions on the plug and in the barrel beingsubstantially equal, an annular retaining ring having a cylindricalportion and an inwardly directed flange portion, said cylindricalportion of said ferrule nesting in a recess in the exterior end portionof said barrel with said flange portion capping the end edge of saidbarrel, the bead on the largest diameter step portion of the plug beingpositioned in partially overlapping relationship with the remote end ofthe cylindrical portion of the ferrule thereby compressing thecorresponding step portion of the barrel into a latching and sealingrelationship with said plug, and a second seal being effected betweenthe barrel and the plug by said bead on the next largest diameterexterior step portion of the plug indenting into the material of thecorresponding interior step portion of the barrel whereby the barrel andplug are securely latched and sealed together.

13. In a writing instrument of the type having a reservoir for markingfluid, a plug and barrel assembly, and a writing means on said barrelassembly comprising: an elongated hollow barrel member having an innerchamber to house the reservoir and being provided with an annular openend portion of resilient material, said barrel having the writing meansmounted on the end opposite said open end portion, a plug member closedat one end and having an annular open end portion coacting with theannular open end portion of the barrel member to make a close mating fittherewith, the open end portion of one of said members having a skirtwith an annular outwardly extending continuous bead shaped similarly tothe contour of the skirt, the open end portion of the other of saidmembers having an annular inner wall portion such that said continuousbead makes a continuously contacting resilient sealing fit thereagainst;and an annular retaining ring positioned about the annular open endportion of said other member to restrain expansion of the underlyinginner wall portion, said ring being positioned between the outwardlyextending bead and the open end of said other member to latch the beadof the one member in sealing relation against the inner wall portion ofthe other member.

101034 OSRI

1. In a writing instrument of the type having a reservoir for markingfluid, a plug and barrel assembly, and a writing means on said barrelassembly, comprising: an elongated hollow barrel having an inner chamberto house the reservoir and being provided with an annular open endportion of resilient material, said barrel having the writing meansmounted on the end opposite said open end portion, the end portionhaving an annular inner wall portion; a plug member closed at one endand having an annular resilient skirt positioned within the open endportion of the barrel and shaped to make a close mating fit within saidannular inner wall portion, said skirt having an annular outwardlyextending continuous bead shaped similarly to the contour of the skirtand making a continuously contacting resilient sealing fit against saidannular inner wall portion; and an annular retaining ring positionedabout the annular open end portion of the barrel to restrain expansionof the underlying inner wall portion, said ring being positioned betweenthe outwardly extending bead and the open end of the barrel to latch thebead of the plug member in sealing relation against the inner wallportion of the barrel.
 2. A plug and barrel assembly as specified inclaim 1 in which the bead is positioned longitudinally inwardly of theopen end of the barrel beyond the position of the retaining ring and inpartially overlapping relation with respect to said ring.
 3. A plug andbarrel assembly as specified in claim 1, in which the skirt portion isprovided with a cylindrical reduced diameter step portion in its outersurface, and the inner wall portion is cylindrically shaped and ofsubstantially the same diameter as said step portion, the outwardlyextending bead being circular and being located intermediate the ends ofsaid cylindrical reduced diameter step portion.
 4. A plug and barrelassembly as specified in claim 1 in which the inner wall portion of thebarrel is provided with interior plural different diameter stepportions, and the annular skirt of the plug is provided exteriorly withcorresponding plural different diameter step portions, the correspondingstep portions being shaped to make a close mating fit of the skirtwithin the open end portion of the barrel.
 5. A plug and barrel assemblyas specified in claim 4 wherein said continuous annular bead is formedon the exterior of one of said step portions of said plug for sealingwith a corresponding interior step portion in the inner wall of saidbarrel.
 6. A plug and barrel assembly as specified in claim 1 whereinthe retaining ring has a cylindrical portion nested in a recess in theexterior surface of the open end portion of the barrel and an integrallyformed, radially inwardly directed flange portion overlying the end edgeof said open end portion of the barrel whereby the latching forcecreated by said bead compresses the material of the end of the barrelgenerally axially against said flange of the ring and generally radiallyagainst the cylindrical portion of said ring.
 7. In a plug and barrelassembly as specified in claim 1 wherein the material of the barrel andplug is plastic and the walls of said barrel are relatively thin.
 8. Awriting instrument having a barrel with one open end and with a writingmeans projecting from the other end, a plug assembled with the open endof said barrel, and means for latching and sealing said plug in the openend of said barrel, said means comprising plural different dIameter stepportions on the exterior of the open end portion of said plug, outwardlyextending continuous beads formed on at least two step portions on saidplug, plural different diameter step portions formed on the interior ofthe open end portion of said barrel, the diameters of the correspondingstep portions on the plug and in the barrel being substantially equal,an annular retaining ring having a cylindrical portion encircling theexterior open end portion of said barrel, the bead on the largestdiameter step portion of the plug being positioned in partiallyoverlapping relationship with the remote end of the cylindrical portionof the ring thereby compressing the corresponding step portion of thebarrel into a latching end sealing relationship with said plug, and asecond seal being effected between the barrel and the plug by said beadon the next largest diameter step portion of the plug indenting into thematerial of the corresponding step portion of the barrel whereby thebarrel and plug are securely latched and sealed together.
 9. A writinginstrument as claimed in claim 8 wherein said ring has a radiallyinwardly directed flange portion overlying the end of the barrel wherebythe latching and sealing created by the bead on the largest diameterstep portion is effected in the material of the barrel by the axial andradial compressive forces created between the flange and cylindricalportions of the retaining ring and said last named bead.
 10. A writinginstrument as claimed in claim 8 wherein the diameter of one stepportion of said plug coincides throughout its length with acorresponding substantially equal in diameter internal portion of saidbarrel whereby sealing against capillary leaking therebetween iseffected.
 11. A writing instrument as claimed in claim 8 wherein thematerial of the barrel and plug is a plastic material and the materialof said retaining ring is a metal material.
 12. In a writing instrumenthaving an elongated, hollow barrel made of plastic material and with oneopen end and with a porous writing nib projecting from the other end, acap frictionally and removably attached to said barrel in coveringrelationship to said writing nib, and a plug made of plastic materialand having one end closed and having the other end open, said open endof the plug being assembled with the open end of said barrel, incombination, means for latching and sealing said open end of said plugin the open end of said barrel, said means comprising plural differentdiameter step portions on the exterior of the open end of said plug, anoutwardly extending continuous bead formed on the largest and nextlargest diameter step portions of said plug, plural different diameterstep portions formed on the interior of the open end portion of saidbarrel, the diameters and axial lengths of the corresponding stepportions on the plug and in the barrel being substantially equal, anannular retaining ring having a cylindrical portion and an inwardlydirected flange portion, said cylindrical portion of said ferrulenesting in a recess in the exterior end portion of said barrel with saidflange portion capping the end edge of said barrel, the bead on thelargest diameter step portion of the plug being positioned in partiallyoverlapping relationship with the remote end of the cylindrical portionof the ferrule thereby compressing the corresponding step portion of thebarrel into a latching and sealing relationship with said plug, and asecond seal being effected between the barrel and the plug by said beadon the next largest diameter exterior step portion of the plug indentinginto the material of the corresponding interior step portion of thebarrel whereby the barrel and plug are securely latched and sealedtogether.
 13. In a writing instrument of the type having a reservoir formarking fluid, a plug and barrel assembly, and a writing means on saidbarrel assembly comprising: an elongated hollow barrel member having aninner chamber to house the reservoir aNd being provided with an annularopen end portion of resilient material, said barrel having the writingmeans mounted on the end opposite said open end portion, a plug memberclosed at one end and having an annular open end portion coacting withthe annular open end portion of the barrel member to make a close matingfit therewith, the open end portion of one of said members having askirt with an annular outwardly extending continuous bead shapedsimilarly to the contour of the skirt, the open end portion of the otherof said members having an annular inner wall portion such that saidcontinuous bead makes a continuously contacting resilient sealing fitthereagainst; and an annular retaining ring positioned about the annularopen end portion of said other member to restrain expansion of theunderlying inner wall portion, said ring being positioned between theoutwardly extending bead and the open end of said other member to latchthe bead of the one member in sealing relation against the inner wallportion of the other member.